Determination of formaldehyde in fruit juice based on magnetic strong cation-exchange resin modified with 2,4-dinitrophenylhydrazine

A method was developed using magnetic strong cation-exchange resin modified with 2,4-dinitrophenylhydrazine (DNPH) for the determination of formaldehyde (HCHO) in fruit juice samples. The procedures of extraction and derivatization were carried out in a single step by stirring the resins and diluted fruit juice with water. When the procedures were completed, the resins adsorbing the HCHO-DNPH derivative were easily separated from the sample matrix by an adscititious magnet. The HCHO-DNPH derivative eluted from the resins was directly determined by high-performance liquid chromatography with UV detector at 360 nm. The limit of detection of the proposed method in fruit juice obtained is 6.0 ng mL^-1. In this work, the volume of fruit juice was 5 mL and the amount of MSCX resins was 100 mg, and the resins can be reused 10 times. The relative standard deviations of intra-day and inter-day ranging from 3.9% to 6.1% and from 4.2% to 7.0% are obtained, respectively. The recovery of HCHO in the analysis of spiked fruit juice samples is in the range of 85.7-100.4%.